Electrical connectors provide signal connections between electronic devices using signal contacts. Often, the signal contacts are so closely spaced that undesirable interference, or “cross talk,” occurs between adjacent signal contacts. As used herein, the term “adjacent” refers to contacts (or rows or columns) that are next to one another. Cross talk occurs when one signal contact induces electrical interference in an adjacent signal contact due to intermingling electrical fields, thereby compromising signal integrity. With electronic device miniaturization and high speed, high signal integrity electronic communications becoming more prevalent, the reduction of cross talk becomes a significant factor in connector design.
One commonly used technique for reducing cross talk is to position separate electrical shields, in the form of metallic plates, for example, between adjacent signal contacts. The shields act to block cross talk between the signal contacts by blocking the intermingling of the contacts' electric fields. Ground contacts are also frequently used to block cross talk between adjacent differential signal pairs. FIGS. 1A and 1B depict exemplary contact arrangements for electrical connectors that use shields and ground contacts to block cross talk.
FIG. 1A depicts an arrangement in which signal contacts (designated as either S+ or S−) and ground contacts G are arranged such that differential signal pairs S+, S− are positioned along columns 101-106. As shown, shields 112 can be positioned between contact columns 101-106. A column 101-106 can include any combination of signal contacts S+, S− and ground contacts G. The ground contacts G serve to block cross talk between differential signal pairs in the same columns The shields 112 serve to block cross talk between differential signal pairs in adjacent columns.
FIG. 1B depicts an arrangement in which signal contacts S and ground contacts G are arranged such that differential signal pairs S+, S− are positioned along rows 111-116. As shown, shields 122 can be positioned between rows 111-116. A row 111-116 can include any combination of signal contacts S+, S− and ground contacts G. The ground contacts G serve to block cross talk between differential signal pairs in the same row. The shields 122 serve to block cross talk between differential signal pairs in adjacent rows.
Because of the demand for smaller, lower weight communications equipment, it is desirable that connectors be made smaller and lower in weight, while providing the same performance characteristics. Shields take up valuable space within the connector that could otherwise be used to provide additional signal contacts, and thus limit contact density (and, therefore, connector size). Additionally, manufacturing and inserting such shields substantially increase the overall costs associated with manufacturing such connectors. In some applications, shields are known to make up 40% or more of the cost of the connector. Another known disadvantage of shields is that they lower impedance. Thus, to make the impedance high enough in a high contact density connector, the contacts would need to be so small that they would not be robust enough for many applications.
U.S. patent application Ser. No. 10/284,966, the disclosure of which is incorporated by reference in its entirety, discloses and claims lightweight, low cost, high density electrical connectors that provide impedance controlled, high-speed, low interference communications, even in the absence of shields between the contacts. It would be desirable, however, if there existed a lightweight, high-speed, mezzanine-style, electrical connector (i.e., one that operates above 1 Gb/s and typically in the range of about 10 Gb/s) that reduces the occurrence of cross talk without the need for ground contacts or internal shields.